Finally I got it fix. Doing some research found that the delring acs bolt spring loose tension over the years and don't know where to find a replacements for discontinued markers I open the bolt and put some shims to make the spring stiffer again and looks like it works, tested on my back yard full hopper on semi, 3 round burst and full and no even one chopped ball. Again thanks shunut for your time and advice. Hopefully this idea help somebody out there with same problem.